This invention relates to a glow plug current supply control system in a diesel engine, and particularly to a glow plug current supply system having a rapid heating circuit and an after glow circuit.
In order to stabilize the combustion in the diesel engine in the cold state to control occurrence of white smoke and sounds of vibrations, there has been used an after glow circuit for supplying current not only during warming-up prior to the start of the engine but also after the start of engine. In this after glow current supply, if a voltage from a power source is directly applied to the glow plug, then the glow plug is heated to an undesired high temperature and the durability of the glow plug is lowered to a considerable extent. Consequently, a resistor is connected to the glow plug in series, so that the voltage applied to the glow plug can be decreased. However, this arrangement is disadvantageous in that an electric power consumed in resistor is high and a resistor is heat to a high temperature. In consequence, when the above-described after glow circuit is provided with the diesel engine, consideration in the aspect of safety is need thus possibly resulting in increased manufacturing cost.